Cooling systems are normally provided on board of a means of transport, for example on board of aircrafts, ships, trains or busses, in order to properly cool components arranged on or carried on board of the means of transport. These components may include components that require preservation, e.g. food, and components which generate heat while operated, like heat generating devices, e.g. electrical or electronic devices and electrical or electronic components.
A cooling system for cooling food on board of an aircraft is, for example, described in DE 43 40 317 A1 and U.S. Pat. No. 5,513,500. The food with which the passengers are to be provided is typically kept in mobile transport containers. These transport containers are equipped and pre-cooled outside of the aircraft and, after being loaded onto the aircraft, set down at appropriate deposit locations in the aircraft passenger compartment, for example in the on-board kitchens. In order to ensure that the food remains fresh until it is distributed to the passengers, cooling stations are provided in the region of the transport container deposit locations, these stations being supplied with cooling energy by a central chiller device and this cooling energy being delivered to the transport containers with the food stored therein. The central chiller device is thermally coupled to the individual cooling stations via a cooling circuit. The cooling circuit comprises a feed line as well as a withdrawal line in which a refrigerant is circulated. The feed line connects the central chiller device to the individual cooling stations in order to feed refrigerant cooled to an appropriately low temperature by the central chiller device and therefore cooling energy to the cooling stations. Refrigerant which has been heated through the delivery of cooling energy to the cooling stations is returned from the cooling stations to the central chiller device via the withdrawal line.
Another cooling system for cooling e.g. food on board of an aircraft is disclosed in DE 10 2006 005 035 B3 and WO 2007/088012 A1. This cooling system comprises a chiller device and a first cooling circuit which is adapted to feed cooling energy generated by the chiller device to at least one cooling station. The chiller device comprises a second cooling circuit which is formed separately from the first cooling circuit and is thermally coupled to the first cooling circuit.
DE 10 2009 011 797 A1 and US 2010/0251737 A1 also describe a cooling system for cooling e.g. food on board of an aircraft. The cooling system comprises a refrigerating device and a cooling circuit. The cooling circuit is devised to supply cooling energy produced by the refrigerating device to at least one cooling station. The refrigerant circulating in the cooling circuit is so selected that upon release of its cooling energy to the at least one cooling station it is convertible from the liquid to the gaseous state and is then convertible back to the liquid state by means of corresponding pressure and temperature control in the cooling circuit.
In known cooling systems (which are also sometimes named supplemental cooling systems) the used cooling agent (also sometimes referred to as refrigerant or cooling fluid to explicitly indicate that a fluid is used) is often cooled down to a low temperature lower than 0° C., e.g. to a temperature of about −9° C. The cooling agent is then supplied to the cooling stations by means of one or more cooling circuits. In case of aircrafts, the cooling stations for cooling the food are often referred to as cooling units or Air Cooling Units (also sometimes referred to as Air Chilling Units) (ACUs). For cooling food the ACUs are normally distributed in on-board kitchens, which are cooled regions.
Heat generating devices, like electronic devices, e.g. electronic devices of the In Flight Entertainment (IFE) system of an aircraft, are normally arranged outside the cooled on-board kitchen regions or other chilled regions. The outer temperature around the means of transport, like an aircraft, can sometimes rise up to 60° C. in hot areas, which also leads to high temperatures at uncooled regions of the means of transport, e.g. the aircraft. Thus, simply providing the ACUs used for cooling food also for cooling other heat generating devices leads to the problem that the power electronics of the ACU generates heat in operation and, in order to prevent the ACU from overheating, the power of the ACU has to be reduced to a lower level.
Known techniques for heat dissipation of the power electronics by means of cooling fins cannot be applied because of the limited space inside the ACUs and the small temperature difference between the outside of the ACUs and the maximally allowed temperature inside the ACUs, which normally lies around 90° C.
It has been conceived to cool said power electronics by means of cold plates, i.e. elements supplied with the cooling agent (cooling fluid) of the supplemental cooling system. If such cold plates are brought into contact with the power electronics, e.g. if the power semiconductors are arranged on the cold plates, the cooling fluid which is supplied at a (very) low temperature, e.g. about −9° C., would cool components or elements of the power electronics down to a temperature below the dew point of the ambient air of the power electronics. This can lead to short-circuits, electric arcs or sparks or other undesirable phenomena in the power electronics.